Watering system problem- syphoning

Emerion · 8 March

Excuse the long explanation, but I think I’m saving a number of questions that I might ask, if I were you. We have a solar powered watering system, for our polytunnel. It uses a submersible pump in one of 2 connected 1000 litre rainwater tanks. This leads, via a hose and piping, to lots of small spray drippers. My problem is that the system constantly syphons water from the tanks and some of the drippers are always gently dripping. It’s surprising how fast the tanks empty with this happening 24/7. The drippers don’t drip evenly when syphoning, so just letting this happen is not a solution. I’m going to try and find a tap to put into the hose that I can manually turn off for most of the time. This is annoying because the “automatic” watering system will now rely on me remembering to turn the tap back on. I thought of using a battery powered water timer to turn off the water from the tank and stop the dripping, but can’t because the pump doesn’t generate enough pressure to force the water through a timer. Also, when we’re away, we’re going to have to use mains water on a timer, otherwise we risk the rainwater tank being syphoned to empty, and the pump then attempting to run on no water, and breaking. We will need a really reliable timer, because I dread to think of the water bill, should it fail physically and spend the best part of 2 weeks allowing metered water to come through it. In case you’re wondering why I bother with the solar powered system at all, we’re in West Wales and get an awful lot of rain. It seems daft to pay for water for the polytunnel, when we have so much of it free. And not good environmentally. However, it doesn’t always rain in Wales, contrary to rumour, and the tank does syphon dry quite often. So I have a couple of questions.

Are there any good quality reliable makes of water timer out there, in your experience, or are they all made as cheaply as possible in China now?
Can anyone suggest another ingenious way to stop the syphoning in the pumped water system?

McRazz · 8 March

I'm not sure i quite follow - Is this a pumped system or a gravitational system that works on some kind of timed valve?

It sounds like you need a solenoid shut off valve to ensure the system opens and closes in line with the timed irrigation programme.

Pictures of the setup will help, or perhaps a schematic.

TheVanguard · 8 March

Sounds like gravity may be the problem… if the open end (or drip end) is lower than the water in the tank then it will empty until it’s the same level…you can check this easily by holding the end low down and seeing it drip and lift it above the tank and see if it stops.

I use an inline valve to stop mine but it’s manual of course..

you might be able to balance it by lifting it high enough so it can’t come out on its own unless the pump is turned on…maybe?

Emerion · 8 March

@McRazz, it’s pumped. But the water drips out even when the pump is off.

McRazz · 8 March

A pump won't shut off the flow so a valve is required. You could mitigate the effect of gravitational siphoning by having your outlet at the base of the reservoir, if you havnt done this already. You could add a tap timer along the line and have it working in sync. These are valve operated.

You could also add a loop in the hose between the reservoir and the emitters in the hope that it creates an small air lock that is formed when the programme ends and cleared when the pump kicks in...

steephill · 8 March

You could make your own battery powered timer and valve setup. There are lots of 12V operating valves and timers which will run off a leisure battery which can be kept topped up by solar panels. Search for "12V water valve" and "12v timer switch" you should find lots of options e.g. Heschen Digital LCD Power Weekly Programmable Timer Relay Switch CN101A DC 12V 16 Amp SPST and Electric Solenoid Valve 12V,1/2" DC 12V Normally Closed Brass Electric for Water Control There are lots of very similar bits of kit to be found on the usual online shops.

Water valves like these and the usual Hozelock and Gardena ready made versions all fail to closed which means that they require power in order to open. Any problem with power like batteries dying means the valves close. There is still the possibility of seals blowing under mains pressure but normal maintenance of seals and ensuring connections are tight make that a rare problem. I would advise using brass connectors rather than plastic.

Your other option is to lower the level of your water storage below the level of your drippers but as that means digging a 2 cu.m. hole it might not be an easy choice.

Emerion · 9 March

@steephill, this sounds interesting. You mention the possibility of failure under mains water pressure. Does this imply that these valves are designed to work with a water supply under mains pressure? I.e. would 12v pump be able to pull the water through from my tank when the valve is open? If so, I’m delighted. 😀

Emerion · 9 March

That’s clever @McRazz Thank you

JennyJ · 9 March

As far as I know, standard watering timers (Gardena, Hozelock, cheaper ones that seem to work just as well) go on the mains outside tap and you put a pressure reducer after the timer to reduce the pressure for the small-bore tubes and drippers. That's how mine is set up anyway. I've had timer failures, once due to to "user error" when I forgot to bring it inside before the cold weather came, and once when the battery leaked and destroyed the connections.

Watering system problem- syphoning

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